http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:228757 A paradigm model system for studying the development of patterned connections in the nervous system is the topographic map formed by retinal axons in the optic tectum/superior colliculus. Starting in the 1970s, a series of computational models have been proposed to explain map development in both normal conditions, and perturbed conditions where the retina and/or tectum/superior colliculus are altered. This stands in contrast to more recent models that have often been simpler than older ones, and tend to address more limited data sets, but include more recent genetic manipulations. The original exploration of many of the early models was one-dimensional and limited by the computational resources of the time. This leaves open the ability of these early models to explain both map development in two dimensions, and the genetic manipulation data that have only appeared more recently. In this article, we show that a two-dimensional and updated version of the XBAM model (eXtended Branch Arrow Model), first proposed in 1982, reproduces a range of surgical map manipulations not yet demonstrated by more modern models. A systematic exploration of the parameter space of this model in two dimensions also reveals richer behavior than that apparent from the original one-dimensional versions. Furthermore, we show that including a specific type of axon-axon interaction can account for the map collapse recently observed when particular receptor levels are genetically manipulated in a subset of retinal ganglion cells. Together these results demonstrate that balancing multiple influences on map development seems to be necessary to explain many biological phenomena in retinotectal map formation, and suggest important constraints on the underlying biological variables. 2011-02-10T00:00:00Z Simpson, Hugh D. og Goodhill, Geoffrey J. http://espace.library.uq.edu.au/view/UQ:254124 2011-10-05T00:00:00Z Akram, Uzma og Milburn, Gerard J. http://espace.library.uq.edu.au/view/UQ:231181 Organic bulk heterojunction photovoltaic devices predominantly use the fullerene derivatives [C60]PCBM and [C70]PCBM as the electron accepting component. This report presents a new organic electron accepting small molecule 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (K12) for organic solar cell applications. It can be processed by evaporation under vacuum or by solution processing to give amorphous thin films and can be annealed at a modest temperature to give films with much greater order and enhanced charge transport properties. The molecule can efficiently quench the photoluminescence of the donor polymer poly(3-n-hexylthiophene-2,5-diyl) (P3HT) and time resolved microwave conductivity measurements show that mobile charges are generated indicating that a truly charge separated state is formed. The power conversion efficiencies of the photovoltaic devices are found to depend strongly on the acceptor packing. Optimized K12:P3HT bulk heterojunction devices have efficiencies of 0.73±0.01% under AM1.5G simulated sunlight. The efficiencies of the devices are limited by the level of crystallinity and nanoscale morphology that was achievable in the blend with P3HT. 2011-03-04T00:00:00Z Schwenn, Paul og Gui, Kurt og Nardes, Alexandre M. og Krueger, Karsten og Lee, Kwan og Mutkins, Karyn og Rubinsztein-Dunlop, Halina og Shaw, Paul Edward og Kopidakis, Nikos og Burn, Paul og Meredith, Paul http://espace.library.uq.edu.au/view/UQ:237155 We report the design, construction and characterization of a 4 mega-pixel, optically-addressed, spatial light modulator (OSLM). The intensity distribution corresponding to a kinoform is displayed across two wide-screen liquid crystal on silicon displays, the images of which are combined and relayed to the address face of a 40 mm aperture OSLM. This spatially varying intensity profile is converted into a phase hologram on the readout side of the OSLM. When illuminated at 532 nm we measure a first-order diffraction efficiency of ≈50% at 400 line pairs and ≈20% at 900 line pairs. We show that aberration associated with the non-flatness of the device can be corrected within software by modification of the hologram. 2011-03-17T00:00:00Z Preece, Daryl og Yao, Eric og Gibson, Graham og Bowman, Richard og Leach, Jonathan og Padgett, Miles http://espace.library.uq.edu.au/view/UQ:265932 We consider the problem of fitting a statistical model to 30 years of sea surface temperature records collected over a large portion of the Northern Atlantic. The observations were collected sparsely in space and time with different levels of accuracy. The purpose of the model is to produce an atlas of oceanic properties, including climatological mean fields, estimates of historical trends, and a spatio-temporal reconstruction of the anomalies, i.e., the transient deviations from the climatological mean. These products are of interest to climate change and climate variability research, numerical modeling, and remote sensing analyses. Our model improves upon the current tools used by oceanographers in that it constructs instantaneous temperature fields before averaging them into the climatology, thus giving equal weight to all years in the time frame, regardless of the temporal distribution of data. It also accounts for nonisotropic and nonstationary space and time dependencies, owing to its use of discrete process convolutions. Particular attention is given to the handling of massive datasets such as the one under study. This is achieved by considering compact support kernels that allow an efficient parallelization of the Markov chain Monte Carlo method used in the estimation of the model parameters. Resulting monthly climatologies are compared with those of the World Ocean Atlas 2001, version 2. Different water masses appear better separated in our climatology, and a close link emerges between the kernels' shape and the dominating patterns of ocean currents. The subpolar and the temperate North Atlantic display opposite trends, with the former mainly cooling over the years and the latter mainly warming, especially in the Gulf Stream region. Long-term changes in annual cycles are also detected. As in any hierarchical Bayesian model, parameter estimates come with credibility intervals, which are useful to compare results with other approaches and detect areas where sampling campaigns are needed the most. 2012-01-24T00:00:00Z Lemos, Ricardo T. og Sanso, Bruno http://espace.library.uq.edu.au/view/UQ:185848 Generalizations of the density matrix renormalization group method have long been sought after. In this paper, we assess the accuracy of projected entangled-pair states on infinite lattices by comparing with quantum Monte Carlo results for several non-frustrated spin- 1/2 systems. Furthermore, we apply the method to a frustrated quantum system. 2009-11-12T00:00:00Z Bauer, B. og Vidal, G. og Troyer, M. http://espace.library.uq.edu.au/view/UQ:252685 The Weibull proportional hazards model is commonly used for analysing survival data. However, formal tests of model adequacy are still lacking. It is well known that residual-based goodness-of-fit measures are inappropriate for censored data. In this paper, a graphical diagnostic plot of Cox–Snell residuals with a simulated envelope added is proposed to assess the adequacy of Weibull survival models. Both single component and two-component mixture models with random effects are considered for recurrent failure time data. The effectiveness of the diagnostic method is illustrated using simulated data sets and data on recurrent urinary tract infections of elderly women. 2011-09-21T00:00:00Z Zhao, Yun og Lee, Andy H. og Yau, Kelvin K.W. og McLachlan, Geoffrey J. http://espace.library.uq.edu.au/view/UQ:222297 2010-11-24T00:00:00Z Brewer, D. og Eayrs, S. og Mounsey, R. og Wang, Y. G. http://espace.library.uq.edu.au/view/UQ:202251 2010-04-09T00:00:00Z Tonkes, E. J. og Isaac, P. S. og Scharaschkin, V. http://espace.library.uq.edu.au/view/UQ:60044 Four sunspot-minimum periods (1963-1966, 1971-1977, 1983-1987 and 1992-1997) have been examined for the results which are presented. Using several different weather parameters, tropospheric gravity waves, enhanced cold fronts and two rainfall data sets in Eastern Australia, associations at reasonably high levels of significance have been found with enhanced geomagnetic activity (EGA). Statistically this EGA involved either short delays of several days or long delays of about 20 days. The geomagnetic parameters used were (a) the AE index (b) the hourly H component for a number of stations and (c) the daily K-P-sum value. The K-P-sum analyses have shown that the EGA associated with the delays form part of four or five cycles of recurrent geomagnetic activity for 27-day periodicities. Furthermore statistically two recurrent cycles are found to exist concurrently, one apparently related to the short delays and the other to the long delays. Periodicities of 13.5 days are created because the two sets are displaced from each other by approximately this interval. A brief reference is made to the 13.5 periodicity known to exist for geomagnetic activity and the evidence in the literature for active regions on the sun to be displaced by 180 degrees of solar longitude. 2007-08-14T00:00:00Z Bowman, GG og Mortimer, IK http://espace.library.uq.edu.au/view/UQ:79386 A stochastic metapopulation model accounting for habitat dynamics is presented. This is the stochastic SIS logistic model with the novel aspect that it incorporates varying carrying capacity. We present results of Kurtz and Barbour, that provide deterministic and diffusion approximations for a wide class of stochastic models, in a form that most easily allows their direct application to population models. These results are used to show that a suitably scaled version of the metapopulation model converges, uniformly in probability over finite time intervals, to a deterministic model previously studied in the ecological literature. Additionally, they allow us to establish a bivariate normal approximation to the quasi-stationary distribution of the process. This allows us to consider the effects of habitat dynamics on metapopulation modelling through a comparison with the stochastic SIS logistic model and provides an effective means for modelling metapopulations inhabiting dynamic landscapes. 2007-08-15T00:00:00Z Ross, JV http://espace.library.uq.edu.au/view/UQ:294099 Astronomical telescopes increasingly operate in surveymode sweeping the sky systematically and producing highly processed data products such as astronomical catalogues which are lists of objects with positional information and other measurements usually including flux in a particular band. An important problem in electronic astronomy is the appropriate way to combine information from different catalogues produced by different telescopes. A key problem in combining this information is to establish different observations of the same object in the two catalogues i.e. the problem of catalogue matching. Positional information is not always sufficient in establishing matches reliably in these cases additional information from the non-positional measurements may also be used. This non-positional information is often scientifically interesting and its inter-catalogue properties may be the main object of study. In previous studies it is argued that while models of non-positional properties may assist in catalogue matching if these properties are scientifically interesting then the conclusions drawn from the analysis may be distorted by using this non-positional information. In this paper it is demonstrated that by employing a predictive Bayesian formalism it is possible to use all available information to assist in obtaining the most reliable matches and still obtain undistorted conclusions. Distortions are avoided because predictive distributions are computed where all the configurations of matches are marginalized over, rather than other approaches which choose a single most likely configuration of matches. 2013-03-18T11:15:39Z Rohde, David og Gallagher, Marcus og Drinkwater, Michael http://espace.library.uq.edu.au/view/UQ:190954 Fernando Rodriguez-Villegas has been studying hypergeometric families of Calabi–Yau manifolds, and from his investigations he has found (numerically) many possible supercongruences. For example, he conjectures for every odd prime p that Image Here, we use the theory of Gaussian hypergeometric series, the properties of the p-adic Γ-function, and a strange combinatorial identity to prove this conjecture. 2009-12-23T00:00:00Z Mortenson, Eric http://espace.library.uq.edu.au/view/UQ:133003 A G-design of order n is a decomposition of the complete graph on n vertices into edge-disjoint subgraphs isomorphic to G. We survey the current state of knowledge on the existence problem for G-designs. This includes references to all the necessary designs and constructions, as well as a few new designs. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 373-410, 2008 2008-03-27T00:00:00Z Adams, P. og Bryant, D. E. og Buchanan, M. J. http://espace.library.uq.edu.au/view/UQ:217314 2010-09-28T00:00:00Z Knittel, J. og Mößner, J. og Bammert, M. http://espace.library.uq.edu.au/view/UQ:200056 Asymmetric steering is an effect whereby an inseparable bipartite system can be found to be described by either quantum mechanics or local hidden variable theories depending on which one of Alice or Bob makes the required measurements. We show that, even with an inseparable bipartite system, situations can arise where Gaussian measurements on one half are not sufficient to answer the fundamental question of which theory gives an adequate description and the whole system must be considered. This phenomenon is possible because of an asymmetry in the definition of the original Einstein-Podolsky-Rosen paradox and in this article we show theoretically that it may be demonstrated, at least in the case where Alice and Bob can only make Gaussian measurements, using the intracavity nonlinear coupler. © 2010 The American Physical Society 2010-03-21T00:00:00Z Midgley, S. L. W. og Ferris, A. J. og Olsen, M. K. http://espace.library.uq.edu.au/view/UQ:203475 2010-04-19T00:00:00Z Midgley, Sarah L. W. og Ferris, Andrew J. og Olsen, Murray K. http://espace.library.uq.edu.au/view/UQ:271019 The asymptotic behavior of S-estimators in a random design linear model with long-range-dependent Gaussian errors is considered. It turns out that the S-estimators of regression parameter and error variance are strongly consistent under mild conditions. Furthermore, the asymptotic distribution of the S-estimator of regression parameter is normal if the design vectors are i.i.d. and is non-normal if the design vectors are long-range dependent Gaussian vectors. We also show that the asymptotic distribution of S-estimator of the error variance is non-normal since the errors are long-range dependent. 2012-03-21T00:00:00Z Lin, Zhengyan og Li, Degui og Chen, Jia http://espace.library.uq.edu.au/view/UQ:77041 We develop results for bifurcation from the principal eigenvalue for certain operators based on the p-Laplacian and containing a superlinear nonlinearity with a critical Sobolev exponent. The main result concerns an asymptotic estimate of the rate at which the solution branch departs from the eigenspace. The method can also be applied for nonpotential operators. 2007-08-15T00:00:00Z Chabrowski, J og Drabek, P og Tonkes, E http://espace.library.uq.edu.au/view/UQ:246846 We consider asymptotic expansion of the nonparametric M-estimator in a fixed-design nonlinear regression model when the errors are generated by long-memory linear processes. Under mild conditions, we show that the nonparametric M-estimator is first-order equivalent to the Nadaraya–Watson (NW) estimator, which implies that the nonparametric M-estimator has the same asymptotic distribution as that of the NW estimator. Furthermore, we study the second-order asymptotic expansion of the nonparametric M-estimator and show that the difference between the nonparametric M-estimator and the NW estimator has a limiting distribution after suitable standardization. The nature of the limiting distribution depends on the range of long-memory parameter α. We also compare the finite sample behavior of the two estimators through a numerical example when the errors are long-memory. 2011-09-01T00:00:00Z Chen, Jia og Li, Degui og Lin, Zhengyan http://espace.library.uq.edu.au/view/UQ:246852 We investigate the asymptotic behavior of a nonparametric M-estimator of a regression function for stationary dependent processes, where the explanatory variables take values in some abstract functional space. Under some regularity conditions, we give the weak and strong consistency of the estimator as well as its asymptotic normality. We also give two examples of functional processes that satisfy the mixing conditions assumed in this paper. Furthermore, a simulated example is presented to examine the finite sample performance of the proposed estimator. 2011-09-01T00:00:00Z Chen, Jia og Zhang, Lixin http://espace.library.uq.edu.au/view/UQ:246855 2011-09-01T00:00:00Z Chen, Jia http://espace.library.uq.edu.au/view/UQ:223208 2010-12-02T00:00:00Z Asmussen, S og Rojas-Nandayapa, L http://espace.library.uq.edu.au/view/UQ:191032 The Pantanal is the world's largest contiguous freshwater wetland spanning Brazil, Bolivia, and Paraguay. It contains the greatest wildlife densities in the Neotropics and was enlisted by all three countries in the Ramsar convention on wetland conservation. The Brazilian government, together the UNESCO's Man and the Biosphere Program, declared a biosphere reserve in the Pantanal in 2000. Other plans to protect the region include expansion of existing reserves and land use regulations following recommendations from the Cerrado-Pantanal priority setting workshop. Here we evaluated how four conservation scenarios complied with the principles of systematic conservation planning and analyzed their representativeness, efficiency, and complementarity using 17 vegetation classes as surrogates for regional biodiversity. We used MARXAN (systematic conservation planning software) to determine the value of the habitat types protected by each conservation scenario. We found that none of the four conservation scenarios met preferred areal targets for protection of habitats, nor did any protect all 17 biodiversity surrogates. The Pantanal Biosphere Reserve provided the best compromise in conservation planning. 2009-12-27T00:00:00Z Lourival, R. og McCallum, H. og Grigg, G. og Arcangelo, C. og Machado, R. og Possingham, H. http://espace.library.uq.edu.au/view/UQ:201980 2010-04-08T00:00:00Z Knittel, Joachim og Richter, Hartmut og Hain, Mathias og Somalingam, Somakanthan og Tschudi, Theo http://espace.library.uq.edu.au/view/UQ:278592 We analyze the low-energy electronic structure of a series of symmetric cationic diarylmethanes, which are bridge-substituted derivatives of Michler’s Hydrol Blue. We use a four-electron, threeorbital complete active space self-consistent field and multi-state multi-reference perturbation theory model to calculate a three-state diabatic effective Hamiltonian for each dye in the series. We exploit an isolobal analogy between the active spaces of the self-consistent field solutions for each dye to represent the electronic structure in a set of analogous diabatic states. The diabatic states can be identified with the bonding structures in classical resonance-theoretic models of cyanine dyes. We identify diabatic states with opposing charge and bond-order localization, analogous to the classical resonance structures, and a third state with charge on the bridge. While the left- and right-charged structures are similar for all dyes, the structure of the bridge-charged diabatic state, and the Hamiltonian matrix elements connected to it, change significantly across the series. The change is correlated with an inversion of the sign of the charge carrier on the bridge, which changes from an electron pair to a hole as the series is traversed. 2012-08-03T18:47:03Z Olsen, Seth og McKenzie, Ross H. http://espace.library.uq.edu.au/view/UQ:174902 We study atom-atom correlations and relative number squeezing in the dissociation of a Bose-Einstein condensate (BEC) of molecular dimers made of either bosonic or fermionic atom pairs. Our treatment addresses the role of the spatial inhomogeneity of the molecular BEC on the strength of correlations in the short time limit. We obtain explicit analytic results for the density-density correlation functions in momentum space, and show that the correlation widths and the degree of relative number squeezing are determined merely by the shape of the molecular condensate. 2009-04-09T00:00:00Z Ögren, Magnus og Kheruntsyan, K. V. http://espace.library.uq.edu.au/view/UQ:181510 We analyze atom-atom correlations in the s-wave scattering halo of two colliding condensates. By developing a simple perturbative approach, we obtain explicit analytic results for the collinear (CL) and back-to-back (BB) correlations corresponding to realistic density profiles of the colliding condensates with interactions. The results in the short-time limit are in agreement with the first-principles simulations using the positive-P representation and provide analytic insights into the experimental observations of Perrin et al. [Phys. Rev. Lett. 99, 150405 (2007)]. For long collision durations, we predict that the BB correlation becomes broader than the CL correlation 2009-09-03T00:00:00Z Ogren, M og Kheruntsyan, K. V http://espace.library.uq.edu.au/view/UQ:180938 The unequivocal detection of entanglement between two distinct matter-wave pulses is a significant challenge that has yet to be experimentally demonstrated. We describe a realistic scheme to generate and detect continuous-variable entanglement between two atomic matter-wave pulses produced via degenerate four-wave mixing from an initially trapped Bose-Einstein condensate loaded into a one-dimensional optical lattice. We perform a comprehensive numerical investigation for fixed condensate parameters to determine the maximum violation of separability and Einstein-Podolsky-Rosen inequalities for field quadrature entanglement, and describe and simulate an experimental scheme for measuring the necessary quadratures. 2009-09-03T00:00:00Z Ferris, Andrew J. og Olsen, Murray K. og Davis, Matthew J. http://espace.library.uq.edu.au/view/UQ:173965 We perform a theoretical analysis of atomic four-wave mixing via a collision of two Bose–Einstein condensates of metastable helium atoms, and compare the results to a recent experiment. We calculate atom–atom pair correlations within the scattering halo produced spontaneously during the collision. We also examine the expected relative number squeezing of atoms on the sphere. The analysis includes first-principles quantum simulations using the positive P-representation method. We develop a unified description of the experimental and simulation results. 2009-04-06T00:00:00Z Perrin, A. og Savage, C. M. og Boiron, D. og Krachmalnicoff, V. og Westbrook, C. I. og Kheruntsyan, K. V. http://espace.library.uq.edu.au/view/UQ:61540 As discussed in the preceding paper [Wiseman and Vaccaro, preceding paper, Phys. Rev. A 65, 043605 (2002)], the stationary state of an optical or atom laser far above threshold is a mixture of coherent field states with random phase, or, equivalently, a Poissonian mixture of number states. We are interested in which, if either, of these descriptions of rho(ss) as a stationary ensemble of pure states, is more natural. In the preceding paper we concentrated upon the question of whether descriptions such as these are physically realizable (PR). In this paper we investigate another relevant aspect of these ensembles, their robustness. A robust ensemble is one for which the pure states that comprise it survive relatively unchanged for a long time under the system evolution. We determine numerically the most robust ensembles as a function of the parameters in the laser model: the self-energy chi of the bosons in the laser mode, and the excess phase noise nu. We find that these most robust ensembles are PR ensembles, or similar to PR ensembles, for all values of these parameters. In the ideal laser limit (nu=chi=0), the most robust states are coherent states. As the phase noise or phase dispersion is increased through nu or the self-interaction of the bosons chi, respectively, the most robust states become more and more amplitude squeezed. We find scaling laws for these states, and give analytical derivations for them. As the phase diffusion or dispersion becomes so large that the laser output is no longer quantum coherent, the most robust states become so squeezed that they cease to have a well-defined coherent amplitude. That is, the quantum coherence of the laser output is manifest in the most robust PR ensemble being an ensemble of states with a well-defined coherent amplitude. This lends support to our approach of regarding robust PR ensembles as the most natural description of the state of the laser mode. It also has interesting implications for atom lasers in particular, for which phase dispersion due to self-interactions is expected to be large. 2007-08-14T00:00:00Z Wiseman, H. M. og Vaccaro, J. A. http://espace.library.uq.edu.au/view/UQ:61542 A laser, be it an optical laser or an atom laser, is an open quantum system that produces a coherent beam of bosons (photons or atoms, respectively). Far above threshold, the stationary state rho(ss) of the laser mode is a mixture of coherent-field states with random phase, or, equivalently, a Poissonian mixture of number states. This paper answers the question: can descriptions such as these, of rho(ss) as a stationary ensemble of pure states, be physically realized? Here physical realization is as defined previously by us [H. M. Wiseman and J. A. Vaccaro, Phys. Lett. A 250, 241 (1998)]: an ensemble of pure states for a particular system can be physically realized if, without changing the dynamics of the system, an experimenter can (in principle) know at any time that the system is in one of the pure-state members of the ensemble. Such knowledge can be obtained by monitoring the baths to which the system is coupled, provided that coupling is describable by a Markovian master equation. Using a family of master equations for the (atom) laser, we solve for the physically realizable (PR) ensembles. We find that for any finite self-energy chi of the bosons in the laser mode, the coherent-state ensemble is not PR; the closest one can come to it is an ensemble of squeezed states. This is particularly relevant for atom lasers, where the self-energy arising from elastic collisions is expected to be large. By contrast, the number-state ensemble is always PR. As the self-energy chi increases, the states in the PR ensemble closest to the coherent-state ensemble become increasingly squeezed. Nevertheless, there are values of chi for which states with well-defined coherent amplitudes are PR, even though the atom laser is not coherent (in the sense of having a Bose-degenerate output). We discuss the physical significance of this anomaly in terms of conditional coherence (and hence conditional Bose degeneracy). 2007-08-14T00:00:00Z Wiseman, H. M. og Vaccaro, J. A. http://espace.library.uq.edu.au/view/UQ:287856 2012-12-23T01:11:47Z Konstantinidis, Gregory O. og Pappa, Melina og Wikstroem, Gustav og Condylis, Paul C. og Sahagun, Daniel og Baker, Mark og Morizot, Olivier og von Klitzing, Wolf http://espace.library.uq.edu.au/view/UQ:265831 2012-01-24T00:00:00Z Dabringhausen, J. og Kroupa, P. og Baumgardt, H. http://espace.library.uq.edu.au/view/UQ:293293 In low-dimensional topology, many important decision algorithms are based on normal surface enumeration, which is a form of vertex enumeration over a high-dimensional and highly degenerate polytope. Because this enumeration is subject to extra combinatorial constraints, the only practical algorithms to date have been variants of the classical double description method. In this paper we present the first practical normal surface enumeration algorithm that breaks out of the double description paradigm. This new algorithm is based on a tree traversal with feasibility and domination tests, and it enjoys a number of advantages over the double description method: incremental output, significantly lower time and space complexity, and a natural suitability for parallelisation. Experimental comparisons of running times are included. 2013-03-10T00:50:22Z Burton, Benjamin A. og Ozlen, Melih http://espace.library.uq.edu.au/view/UQ:243060 In low-dimensional topology, many important decision algorithms are based on normal surface enumeration, which is a form of vertex enumeration over a high-dimensional and highly degenerate polytope. Because this enumeration is subject to extra combinatorial constraints, the only practical algorithms to date have been variants of the classical double description method. In this paper we present the first practical normal surface enumeration algorithm that breaks out of the double description paradigm. This new algorithm is based on a tree traversal with feasibility and domination tests, and it enjoys a number of advantages over the double description method: incremental output, significantly lower time and space complexity, and a natural suitability for parallelisation. 2011-06-29T07:23:43Z Burton, Benjamin A. og Ozlen, Melih http://espace.library.uq.edu.au/view/UQ:166432 2009-03-06T00:00:00Z Hart, V. G. http://espace.library.uq.edu.au/view/UQ:229645 2011-02-20T00:00:00Z Stephenson, AP og Micolich, AP og Lee, KH og Meredith, P og Powell, BJ http://espace.library.uq.edu.au/view/UQ:271142 A two points Taylor’s formula for the generalised Riemann integral and various bounds for the remainder are established. Moreover, particular instances of interest are given. 2012-03-22T00:00:00Z Dragomir, S. S. og Thompson, H. B. http://espace.library.uq.edu.au/view/UQ:287420 A two-state model Hamiltonian is proposed, which can describe the coupling of twisting displacements to charge-transfer behavior in the ground and excited states of a general monomethine dye molecule. This coupling may be relevant to the molecular mechanism of environment-dependent fluorescence yield enhancement. The model is parameterized against quantum chemical calculations on different protonation states of the green fluorescent protein chromophore, which are chosen to sample different regimes of detuning from the cyanine (resonant) limit. The model provides a simple yet realistic description of the charge transfer character along two possible excited state twisting channels associated with the methine bridge. It describes qualitatively different behavior in three regions that can be classified by their relationship to the resonant (cyanine) limit. The regimes differ by the presence or absence of twist-dependent polarization reversal and the occurrence of conical intersections. We find that selective biasing of one twisting channel over another by an applied diabatic biasing potential can only be achieved in a finite range of parameters near the cyanine limit. 2012-12-16T00:56:50Z Olsen, Seth og McKenzie, Ross H. http://espace.library.uq.edu.au/view/UQ:180737 Discoveries of ratios whose values are constant within broad classes of materials have led to many deep physical insights. The Kadowaki–Woods ratio (KWR; refs 1, 2) compares the temperature dependence of a metal's resistivity to that of its heat capacity, thereby probing the relationship between the electron–electron scattering rate and the renormalization of the electron mass. However, the KWR takes very different values in different materials3,4. Here we introduce a ratio, closely related to the KWR, that includes the effects of carrier density and spatial dimensionality and takes the same (predicted) value in organic charge-transfer salts, transition-metal oxides, heavy fermions and transition metals—despite the numerator and denominator varying by ten orders of magnitude. Hence, in these materials, the same emergent physics is responsible for the mass enhancement and the quadratic temperature dependence of the resistivity, and no exotic explanations of their KWRs are required. 2009-09-03T00:00:00Z Jacko, A. C. og Fjaerestad, J. O. og Powell, B. J. http://espace.library.uq.edu.au/view/UQ:196128 2010-02-21T00:00:00Z Tang, Liangdan og Yang, Junzheng og Ng, Shu-Kay og Rodriguez, Noah og Choi, Pui-Wah og Vitonis, Allison og Wang, Kui og McLachlan, Geoffrey J. og Caiazzo, Robert J. og Liu, Brian C.-S. og Welch, Brian C.-S. og Cramer, Daniel W. og Berkowitz, Ross S. og Ng, Shu-Wing http://espace.library.uq.edu.au/view/UQ:249465 Flow cytometry is widely used for single cell interrogation of surface and intracellular protein expression by measuring fluorescence intensity of fluorophore-conjugated reagents. We focus on the recently developed procedure of Pyne et al. (2009, Proceedings of the National Academy of Sciences USA 106, 8519-8524) for automated high- dimensional flow cytometric analysis called FLAME (FLow analysis with Automated Multivariate Estimation). It introduced novel finite mixture models of heavy-tailed and asymmetric distributions to identify and model cell populations in a flow cytometric sample. This approach robustly addresses the complexities of flow data without the need for transformation or projection to lower dimensions. It also addresses the critical task of matching cell populations across samples that enables downstream analysis. It thus facilitates application of flow cytometry to new biological and clinical problems. To facilitate pipelining with standard bioinformatic applications such as high-dimensional visualization, subject classification or outcome prediction, FLAME has been incorporated with the GenePattern package of the Broad Institute. Thereby analysis of flow data can be approached similarly as other genomic platforms. We also consider some new work that proposes a rigorous and robust solution to the registration problem by a multi-level approach that allows us to model and register cell populations simultaneously across a cohort of high-dimensional flow samples. This new approach is called JCM (Joint Clustering and Matching). It enables direct and rigorous comparisons across different time points or phenotypes in a complex biological study as well as for classification of new patient samples in a more clinical setting. 2011-09-10T00:00:00Z Pyne, Saumyadipta og Hu, Xinli og Wang, Kui og Rossin, Elizabeth og Lin, Tsung-I og Maier, Lisa og Baecher-Allan, Clare og McLachlan, Geoffrey og Tamayo, Pablo og Hafler, David og De Jager, Philip og Mesirov, Jill http://espace.library.uq.edu.au/view/UQ:179605 Flow cytometric analysis allows rapid single cell interrogation of surface and intracellular determinants by measuring fluorescence intensity of fluorophore-conjugated reagents. The availability of new platforms, allowing detection of increasing numbers of cell surface markers, has challenged the traditional technique of identifying cell populations by manual gating and resulted in a growing need for the development of automated, high-dimensional analytical methods. We present a direct multivariate finite mixture modeling approach, using skew and heavy-tailed distributions, to address the complexities of flow cytometric analysis and to deal with high-dimensional cytometric data without the need for projection or transformation. We demonstrate its ability to detect rare populations, to model robustly in the presence of outliers and skew, and to perform the critical task of matching cell populations across samples that enables downstream analysis. This advance will facilitate the application of flow cytometry to new, complex biological and clinical problems. 2009-08-06T00:00:00Z Pyne, S. og Hu, X. og Wang, K. og Rossin, E. og Lin, T.-I. og Maier, L. M. og Baecher-Allan, C. og McLachlan, G. J. og Tamayo, P. og Hafler, D. A. og De Jager, P. L. og Mesirow, J. P. http://espace.library.uq.edu.au/view/UQ:274437 A novel method using resistive pulse sensors for electrokinetic surface charge measurements of nanoparticles is presented. This method involves recording the particle blockade rate while the pressure applied across a pore sensor is varied. This applied pressure acts in a direction which opposes transport due to the combination of electro-osmosis, electrophoresis, and inherent pressure. The blockade rate reaches a minimum when the velocity of nanoparticles in the vicinity of the pore approaches zero, and the forces on typical nanoparticles are in equilibrium. The pressure applied at this minimum rate can be used to calculate the zeta potential of the nanoparticles. The efficacy of this variable pressure method was demonstrated for a range of carboxylated 200 nm polystyrene nanoparticles with different surface charge densities. Results were of the same order as phase analysis light scattering (PALS) measurements. Unlike PALS results, the sequence of increasing zeta potential for different particle types agreed with conductometric titration. 2012-05-21T22:46:01Z Vogel, Robert og Anderson, Will og Eldridge, James og Glossop, Ben og Willmott, Geoff http://espace.library.uq.edu.au/view/UQ:268824 We introduce a variational approach for the quantum inverse scattering method to exactly solve a class of Hamiltonians via Bethe ansatz methods. We undertake this in a manner which does not rely on any prior knowledge of integrability through the existence of a set of conserved operators. The procedure is conducted in the framework of Hamiltonians describing the crossover between the low-temperature phenomena of superconductivity, in the Bardeen–Cooper–Schrieffer theory, and Bose–Einstein condensation. The Hamiltonians considered describe systems with interacting Cooper pairs and a bosonic degree of freedom. We obtain general exact solvability requirements which include seven subcases that have previously appeared in the literature. 2012-03-02T11:55:04Z Andrew Birrell og Isaac, Phillip og Links, Jon R. http://espace.library.uq.edu.au/view/UQ:240975 We present a very fast algorithm for general matrix factorization of a data matrix for use in the statistical analysis of high-dimensional data via latent factors. Such data are prevalent across many application areas and generate an ever-increasing demand for methods of dimension reduction in order to undertake the statistical analysis of interest. Our algorithm uses a gradient-based approach which can be used with an arbitrary loss function provided the latter is differentiable. The speed and effectiveness of our algorithm for dimension reduction is demonstrated in the context of supervised classification of some real high-dimensional data sets from the bioinformatics literature. © 2011 Elsevier B.V. 2011-05-18T00:00:00Z Nikulin, V og Huang, TH og Ng, SK og Rathnayake, SI og McLachlan, GJ http://espace.library.uq.edu.au/view/UQ:190347 We demonstrate a wavelength-tunable, fiber-coupled source of polarization- entangled photons with extremely high spectral brightness and quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization Sagnac interferometer we detect a spectral brightness of 273000 pairs (s mW nm)−1, a factor of 28 better than comparable previous sources while state tomography showed the two-photon state to have a tangle of T = 0.987. This improvement was achieved by use of a long crystal, careful selection of focusing parameters and single-mode fiber coupling. We demonstrate that, due to the particular geometry of the setup, the signal and idler wavelengths can be tuned over a wide range without loss of entanglement. 2009-12-17T00:00:00Z Fedrizzi, Alessandro og Herbst, Thomas og Poppe, Andreas og Jennewein, Thomas og Zeilinger , Anton http://espace.library.uq.edu.au/view/UQ:282368 The growth and guidance of axons is an undertaking of both great complexity and great precision, involving processes at a range of length and time scales. Correct axonal guidance involves directing the tips of individual axons and their branches, interactions between branches of a single axon, and interactions between axons of different neurons. In this chapter, we describe examples of models operating at and between each of these scales. 2012-09-24T10:53:15Z Mortimer, Duncan og Simpson, Hugh D. og Goodhill, Geoffrey J. http://espace.library.uq.edu.au/view/UQ:201605 Guidance of axons by molecular gradients is crucial for wiring up the developing nervous system. It often is assumed that the unique signature of such guidance is immediate and biased turning of the axon tip toward orawayfrom the gradient. However,hereweshow that such turning is not required for guidance. Rather, by a combination of experimental and computational analyses, we demonstrate that growth-rate modulation is an alternative mechanism for guidance. Furthermore we show that, although both mechanisms may operate simultaneously, biased turning dominates in steep gradients, whereas growth-rate modulation may dominate in shallow gradients. These results suggest that biased axon turning is not the only method by which guidance can occur. 2010-04-04T00:00:00Z Mortimer, D og Pujic, Z og Vaughan, T og Thompson, AW og Feldner, J og Vetter, I og Goodhill, GJ